1. Field of the Invention
This invention relates generally to data communications and more particularly to digital filters for removing noise from input data bits.
2. Description of the Related Art
Modern data communication devices generally utilize filters to filter out unwanted signals such as noise, false transitions, etc. For example, conventional filters such as LC circuits have been widely used to filter signals. However, LC circuits are typically very complex and expensive to implement in integrated circuit (IC) chips due to the inductors in the LC circuits.
An improved filter using only digital circuits is described, for example, in U.S. Pat. No. 5,789,969 entitled “Digital Delay Circuit and Method” by Barry Davis et al. In this patent, a digital blanking filter is used to compensate for delay variations caused by variations in process, temperature, and voltage. However, the digital blanking filter may sense the first signal transitions falsely because noise may be additive. At high frequencies and long transmission paths, the filter may not be able to filter signals effectively.
Some filters also may use oversampling techniques to sample a signal at a higher frequency. However, oversampling often injects noise such as single bit noise or burst noise in the process. In such cases, conventional digital filters may not be able to remove the noise efficiently.
In view of the foregoing, it would be desirable to have a digital filter that can efficiently filter both single bit noise and burst noise and that can be implemented in an IC chip in a cost effective manner.